This invention relates to an electronic lock system and, more particularly, to an electronic switch for use with a data combination card having a binary code indicator distributed over the surface thereof and operable to actuate a door lock in response to the insertion of the data card in the switch system.
This invention has particular application to use in buildings, such as hotels, having large numbers of rooms required to be locked, and is intended to replace the conventional mechanical lock and key system now in general use. However, it will be understood that the system of this invention could be used with any building or enclosure requiring a locked door, such as safedeposit boxes or automobiles.
In typical electronic systems for controlling entrance to protected areas, a door is provided with an electronic lock which responds to a preselected binary code or combination contained on a key which frequently takes the form of a card. A person wishing to gain entrance through the door inserts his card into a receptacle associated with the lock and the lock circuitry actuates the bolt if the card is correctly coded. Such electronic locks have very significant advantages as compared with conventional lock systems, such as the very large number of code combinations which are available on a card of very small size.
The general inflexibility of the mechanical lock and key systems currently in use prohibits the convenient changing of locks, combinations or key settings. Therefore, a large number of keys are normally issued thus presenting a security problem. Some electronic systems which have attempted to overcome these deficiencies employ a central control unit electrically connected to each of the many individual doors to remotely set and change the individual lock combinations, sense the coding on a card inserted at the various remote door locations, and initiate the bolt action on the remote door locks. One apparent disadvantage of such systems is the susceptibility to failure of all locks if the central control unit is inoperable. In addition, electrically wiring all individual locks to the central control unit is expensive and often inconvenient, especially in older buildings.
In other electronic systems where the central control unit is not employed, the individual lock combinations on each door must be individually changed by manually resetting the switches or changing electrical connections before a new card will operate the lock. Where this system is employed in a hotel, a large expenditure of time by authorized personnel is required each day to change lock combinations for those rooms which are to receive a new occupant.
In addition, the mechanical latch portion of previous electronic lock systems typically requires large amounts of energy to actuate the locks by pulling the bolt back against a spring or the like. Such systems have been considered necessary in the past since it is desirable to employ the conventional rotating handle inside the door to withdraw the bolt without employing a card. The large energy requirements, however, necessitate inconvenient and expensive connection to a high energy source. One solution has been to employ a rotating handle on the outside which will only operate when a correctly coded card is inserted. This, however, defeats the dead bolt feature by providing a mechanical linkage through the outside of the lock which if forceably removed provides a ready means for manually retracting the bolt. Furthermore, such systems frequently do not incorporate a dead bolt feature but employ spring-loaded bolts to allow the bolt to be retracted when the door is being closed and extended again after the door is closed.